- QT duration corrected for heart rate (QTc) >480 ms. QTcF is the recommended correction factor for all sites. If QT duration corrected for heart rate by Fridericia's formula (QTcF) is not possible to obtain or calculate, QT duration corrected for heart rate by Bazett's formula (QTcB) or machine or manual over read, may be obtained after consultation with the medical monitor. The QT correction formula used to determine inclusion and discontinuation should be the same throughout the study.